Test Details
Methodology
Fujirebio Lumipulse chemiluminescent enzyme immunoassay (CLEIA)
Result Turnaround Time
7 days
Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.
Test Includes
This test includes pTau-217/AB42 Ratio; pTau-217 and Beta-amyloid 42.
Use
The pTau-217/Beta Amyloid 42 Ratio aids in the identification of amyloid-related pathology, which is associated with Alzheimer’s disease at a performance level that is consistent with amyloid PET. Both markers, pTau-217 and Beta Amyloid 42, have been well-documented indicators of pathological changes associated with Alzheimer’s disease. Their measurements, in ratio, provide a higher level of sensitivity and specificity than pTau-217 or Beta Amyloid 42/40 Ratio alone. The performance of this test meets the criteria for a confirmatory test as defined by an international consortium of Alzheimer’s experts.1
Clinical cutoff values were established using samples from a well-established patient cohort characterized with amyloid PET data. Values obtained with different laboratory methodologies cannot be used interchangeably. The cutoff values are as follows:
• Low: <0.0086. A low ratio is consistent with a negative (normal) amyloid-positron emission tomography (PET) scan result. This result aids in the exclusion of amyloid-related pathology associated with Alzheimer disease.
• Intermediate: 0.0086 – 0.0152. An intermediate pTau-217/Beta Amyloid 42 Ratio should be interpreted within the context of all clinical findings in symptomatic patients. Additional testing such as amyloid-positron emission tomography (PET) imaging or cerebrospinal fluid (CSF) biomarker assays is recommended to aid in further identification or exclusion of amyloid-related pathology associated with Alzheimer’s disease.
• High: >0.0152. A high ratio is consistent with a positive (abnormal) amyloid-positron emission tomography (PET) scan result. This result aids in the identification of amyloid-related pathology associated with Alzheimer's disease. In the proper clinical context, this test is supportive of Alzheimer'a disease being related to current clinical symptoms.
This test has been validated in symptomatic patients presenting with cognitive impairment symptoms and should be used in context with all clinical findings, including other lab tests, cognitive exams and family history. This test should not be used in asymptomatic individuals.
Special Instructions
This test currently is not approved for use in New York state.
Limitations
This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.
Specimen Requirements
Specimen
Plasma, frozen
Volume
1 mL
Minimum Volume
0.75 mL (Note: This volume does not allow for repeat testing.)
Container
Lavender-top (EDTA) tube
Collection Instructions
Draw full lavender-top (EDTA) tube of blood. Immediately separate plasma from blood via centrifugation (>1500g for 10 minutes) within 40 minutes after blood collection. Transfer plasma to Labcorp polypropylene transport tube, seal and freeze.
Stability Requirements
Temperature | Period |
|---|---|
Room temperature | 40 minutes |
Refrigerated | 6 hours |
Frozen | -10 C: 24 hours <-60 C: 14 days |
Freeze/thaw cycles | Stable x1 |
Storage Instructions
Plasma sample may be stored for up to 24 hours at < -10°C (standard freezer) prior to placing in dry ice (for shipment), or samples may be stored in the refrigerator for up to six hours but then must be placed on dry ice for transport. All samples must be placed on dry ice for transport and must be maintained on dry ice or similar temperatures when reaching the local lab.
Causes for Rejection
Hemolysis; lipemia; heat-treated specimen; gross bacterial contamination; wrong tube type; not stored at proper temperature
Footnotes
- Schindler SE, Galasko D, Pereira AC, et al. Acceptable performance of blood biomarker tests of amyloid pathology—recommendations from the Global CEO Initiative on Alzheimer’s Disease. Nat Rev Neurol. 2024 Jul;20(7):426-439. PubMed 38866966